Genetic Arms Race: Roundworms Use Sex to Outcompete Parasites

A recent report published in the journal Science provides a fascinating example that highlights the advantages of sexual reproduction over asexual reproduction.

The study found that roundworms (C. elegans) that can reproduce either sexually or asexually choose to mostly reproduce asexually when they're healthy. However, when they're infected with a parasite that evolves, the majority of them seek out sex partners to reproduce sexually to boost their genetic diversity so that they're more likely to produce offspring that can withstand the parasites.

The scientists also genetically engineered one population of roundworms to only produce asexually and another population to only reproduce sexually. The asexual population was decimated by the evolving parasites while the sexual population lasted much longer.

Scientists have long known that sexual reproduction give organisms genetic diversity. When their diverse offspring encounters a new threat, the ones genetically equipped to deal with the threat thrive and reproduce more, thus adapting the gene pool of the entire species.

The recent Science study highlights the reality of genetic arms races between species that threaten each other. That is, parasites evolve to exploit the vulnerabilities of the host roundworms and the host roundworms counter-evolve to combat the new capabilities of the parasites.

The concept can presumably have wider implications. For example, the genetics arms race can occur between a hunter and a prey in a battle to genetically one-up each other. Or, it can happen between species competing for the same habitats or food sources.

All things equal, the sexual species will always have the genetic advantage over the asexual species.

Of course, sexual reproduction comes with its potential pitfalls and dangers, such as the imbalance of genders, the difficulty of finding a mate (for solitary animals), mishaps in the mating ritual, and sexual transmitted diseases.

However, for most non-microscopic animals, it seems sexual production is worth braving the inconveniencies and risks of sex.

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